Improvement in targets for surveyors



T. nAvnzs'.

' Target for Surveyoys.

Patented Jan. 26, I875.

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UNITED STATES PATENT QFFIC-E.

THOMAS DAVIES, OF CINCINNATI, OHIO.

IMPROVEMENT lN TARGETS FOR SURVEYORS.

Specification forming part of Letters Patent No. 159,021, dated January 26, 1875; application filed June 19, 1874.

To all whom it may concern Be it known that I, THOMAS DAvlEs, of Cincinnati, Hamilton county, Ohio, have invented a new and useful Target for Surveyors, of which the following is a specification The object of my invention is to furnisha target which will indicate to the surveyor whether the staff is perfectly vertical, and more particularly to indicate any inclination of said staif toward or from the observer, on the line of vision.

In the accompanying drawings, Figure 1 is a perspective view of my improved form of target, detached from the staff. Fig. 2 is a horizontal section of the target. Figs. 3 and 4 show the target in position, the staif being inclined away from the observer in Fig. 3, and toward the observer in Fig. 4.

-A represents a target, such as ordinarily used by surveyors, and having the customary scale B, loop or staple 0, spring D, and retaining-screw E.

My improvement consists in the provision, upon the face of such target, of a horizontal ledge or projection, F, preferably of the represented, or approximately, triangular shape. This plate may be secured to the target by means of screws g g, which pass through lugs G G, or by any other approved means. This plate should occupy the horizontal diameter of the target, from whose face its apex f may have any suitable projection. A projec tion of from two to three inches will be found sufficient for most purposes.

The operation of my improvement is as follows If the staff H is held perfectly vertical, and is not allowed to lean toward or away from the surveyor, nor to incline either to the right or to the left, the cross-lines 0f the theodolite or level will center directly on the apex f of plate F, whose edge only will be .visible, and will appear coincident with the horizontal line of the instrument, as indicated by dotted lines in Fig. 1. In case the staff should be out of plumb, and so as to lean away from the surveyor, the horizontal hair of the theodolite or level will then strike below the apex f, or on the under side of plate F, as indicated by dotted lines in Fig. 3. If, on the contrary, the assistant should hold the staff so as to incline it toward the observer, the horizontal line of the instrument will then be apparent above the apex f, or 011 the upper side of the plate F, as shown by dotted lines in Fig. 4. When the horizontal hair appears in either of the above positions, it' at once indicates to the surveyor that the staff is out of plumb, and in what direction, and he has only to give the proper signal to his assistant to adjust the staff until the hair is focussed on the apex f. Any deflection to right or left is at the same time corrected by the target quarterings, in the usual way, which being accomplished, the surveyor knows that his staff is vertical,and he can then proceed with I his levels with perfect confidence.

In the drawings, the projecting member F is represented as a solid plate but it is evident that a triangular open projection maybe substitutcd therefor, or a portion of the rear edge of the plate may be coved out, as indicated by dotted lines in Fig. 2. The solid plate is, however, preferred, because it affords a more extended surface for exposing the position of the horizontal hair of the instrument. Instead of being triangular, the plate F may be semicircular, semi-elliptical or rectangular, and a notch or other means of indicating the center may be employed, instead of the apex f. The plate F may be gilded, nickel-plated, or colored diversely on its different surfaces. The plate F, instead of being rigidly attached to the face of the target, as shown, may be hinged to the same, and held to its horizontal condition by a spring-catch, and afterward folded down for convenient package or trans portation.

I claim as my invention- The plate F f, arranged upon and projecting horizontally from the front of a surveyors target, in the manner herein described, and for the purpose designated.

In testimony of which invent-ion I hereunto set my hand.

THOMAS DAVIES. Attest:

Gno. H. KNIGHT, JAMES H. LAYMAN. 

